Dynamics of Nanosatellite Deorbit by Bare Electrodynamic Tether in Low Earth Orbit

摘要

This paper studies the dynamics of nanosatellite deorbit by a bare electrodynamic tether. The orbital dynamics of the tethered nanosatellite is modeled in Gaussian perturbation equations and the motion-induced voltage-current relationship along the electrodynamic tether is analyzed by using the 2000 International Geomagnetic Reference Field model including up to seventh-order terms and the International Reference Ionosphere 2007 model. The analysis reveals that the high-order magnetic model of Earth affects the dynamic characteristics of the tethered nanosatellite, especially in orbits with high inclination angles, by changing its orbit from circular to elliptical forms. This is beneficial for deorbiting the nanosatellite in near-polar orbits where the electrodynamic force is not as effective as in the equatorial orbit because the denser atmosphere at a lower perigee will provide a larger atmospheric drag. Moreover, the analysis shows that the electrodynamic force is always against the satellite motion in low Earth orbit even when the induced voltage/current across the tether reverses their polarities in near-polar orbits. Compared to the deorbit rate by the atmospheric drag only, the deorbit rate by an electrodynamic tether will be increased by several orders in magnitudes in both equatorial and polar orbits.